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ivTTnn STATns PATENT @FFICE.

ISAAC SHIMWELL MODOUGALL, OF IRK VALE, CHADDERTON, NEAR MANCHESTER, COUNTY OF LANCASTER, ENGLAND. I

PRODUCTION OF SULPHUROUS ACID.-

SPECIFICATION forming part of Letters Patent No. 311,595, dated February 3, 1885. Application filed September 22, 1883. (No model.) Patented in England March 13, 1883, No. 1,349.

To (tZZ whom it may concern:

Be it known that I, ISAAC SHIMWELL Mo- DOUGALL, a subject of the Queen of Great Britain, and residing at Irk Vale, Ohadderton, near Manchester, in the county of Lancaster, England, have invented certain improvements in the production of sulphurous acid or salts or solutions containing sulphurous acid, and in the mode of applying the same to the treat ment of wood pulp and other purposes, (for which I have obtained a patent in Great Britain No. 1,349, dated March 13, 1883,) of which the following specification is a full description.

Solutions of sulphurous acid and sulphites and bisulphites of alkaline earths have been produced to be employed in the production of pulp by burning sulphur compounds with the oxygen of the air and conducting the sulphurous-acid gas produced upward through a tower or vertical column containing suitable material to diffuse the gas when it is brought into contact with water or alkaline solutions passing down over the diffusing material. This means of production is inconvenient, as in such towers it is difficultto condense the whole of the gas or to produce solutions of regular strength, and considerable nuisance is. sometimes caused by the escape of gases.

By means of my improvements I produce sulphurous acid or solutions containing sulphurous acid or sulphite or bisulphite or other solutions or other salts without employing condensing towers or columns. I accomplish this by burning sulphur or pyrites or spent oxide of iron or other suitable sulphur compounds in stronginclosed vessels, into which, alter igniting the sulphur or its compounds, I force air by any suitable mechanical means, such as an air-pump or fan of sufficient power to drive the sulphurousacid gas through suitable pipes or connections into a vessel or series of vessels containing water or solutions of alkalies or alkaline earths,with which itis desired the gas shall be brought into contact for the purpose of obtaining products containing sulphurous acid; or, when preferable, I force the air or gas forward by suction by suitably placing the air-pump or fan for that purpose;

the retort sufficient to prevent the volatilization of the sulphur, and this I prefer to do by surrounding with water the vessel or vessels in which the sulphur is burned and the pipes or connections carrying the sulphurous gas, for

the same. Complete control is maintained over the sulphurous-acid gas, the gas being conveyed to a distance down below the surface of the liquor or solutions or materials in the vessel or series of vessels, the pressure forcing the same through the contents of the said vessel or vessels. The gas, or solutions of it or sulphite or bisulphite solutions or other salts or mixtures of them, may be prepared of any strength and in any quantities desired for employment in the treatment of pulp, or for other purposes.

The accompanying drawings illustrate what are regarded as the best means for successfully carrying out the process, Figures 1 and 1 taken together showing in elevation a complete apparatus for the purpose.

A represents a blowing-engineto blow air with sufficient force through suitable vessels, B, containing sulphur or sulphur compounds. As the air comes in contact with the sulphur under considerable pressure (after the sulphur has become ignited by applying a red-hot iron internally, or by other suitable means within the vessel) no external heat is needed, but the vessel is required to be immersed in water to prevent the heat becoming too great, or

sublimation would take place, which would stop and spoil the working of the process. The gases then pass through pipes cased with suitable jackets, B, containing water to cool the gases as they are conveyed forward. The gases are then conveyed by the pipes G into suit-able vats or vessels, E, in which are fixed vertical agitators H,to keep the liquor or sedi ment in motion to be more readily acted upon by the passing gases. The vats are connected together at the bottom by passages with stoptaps S, which are always kept closed while the process of blowing the gases is in operation. A pipe with a tap, T, is a means of inlet for the solutions required to be acted upon in the vats. By the regulation of the taps of the .55 the purpose of reducing the temperature of 50 In all cases I maintain a low temperature in passages S and T the liquor can be regulated, 10o

through this continued as desired.

means of exit.

as desired, inthe yats when the process of blowing is stopped, as desired. Before the process of blowing is commenced the vats are filled considerably above the opening of the inlet-pipes C, so that the gases have to pass I head of pressure of solution. On the last vessel is an outlet-pipe, D, to carry away the waste gases. Upon each vat or vessel is placed a gage-glass, G, with suitable taps to 'show'the height ofthe solutions in the vats, and from which samples can be readily taken to show when the solutions are saturated. When the solution in vat No. 1 becomes sufficiently saturated, the blowing is discontinued and the contents of vat No. l emptied to be used for the purpose required. After No. l vat is emptied the taps are opened and the whole of the vats filled to a convenient height, the blowing being continued until the first vat is again saturated, and so the process being The gases pass from vat Ito vat II, and then to vat III, and through as many other vats in like manner as may be found sufficientto absorb thesulphurousacid gases, and at the last vat the waste gases pass through the exit-pipe process is essentially tion, in which the D to a chimney or other I observe, in conclusion, that means of air under blower, and is consequently independent of the .reaction for producing the sulphurous acid, is suificient to overcome the back-press ure of the liquid through which the mixed sulphurous gases from the retort have to pass.

In the old process above referred to the press- V me in the absorbing vessels is maintained by cocks and valves, and the sulphurous gases do not pass through a large body of liquid, but meet the thin streams of liquid filtering over the gravel in the tower.

I claim 'The method of producing sulphurous acid by forcing air under pressure into a close ves sci or retort containing ignited sulphur or sulphur-bearing material, andmaintaining a low 1 temperature in said vessel or retort by surroundingthe same with a cooling medium such as water-and conducting thesulph'u rous gases from said retort into and below the surface of an absorbing liquid in one vessel or a series, where itis allowed to escape, substantially as described. 1 In testimony whereofl have signed my name to this specification in the presence of two subseribing' witnesses.

ISAAC SIIIZIIWELL MODOUGALL.

Witnesses:

CHAS. HULME, 68 Port Street, Jllcmehester, Cashier.

JOSEPH H. PETERS, l9 lllozmt Street, llItMZC/IGSZW', Clerk with I. T.

Doyle, U. 8'. Vice and Deputy Consul.

being assisted by 

